The present invention relates to heating devices for a printed web in a printing press.
In the past, printing presses have been utilized to print colored or black inks on opposed sides of a paper web. Such inks usually comprise a vehicle composed of a resin and a solvent, along with a colored pigment and other additives. During offset printing water is added to the ink and paper.
After printing of the web has taken place, it is necessary to remove the water and a large portion of the solvent from the ink in order to change the viscosity of the ink and set the ink containing the pigment. Presently, relatively long tunnels have been utilized in order to heat set the inks utilizing hot air convection in the tunnels which supply the necessary heat transfer to heat set the inks. However, during convection heating an air barrier is formed between the web and heat source, and the barrier significantly slows down the solvent release. However, such air convention heating is relatively inefficient and slow. Heating the web and removing the solvents thus requires excessively long tunnels and unnecessary expenditure of energy in order to heat set the inks. Further, if shorter tunnels for convention heating are utilized to heat the web, then the speed of the press and associated web must be lowered in order to obtain the necessary heating, and thus such air convention heating devices also place limitations on the speed of the web and press. Also, such long tunnels are unduly costly and an excessive amount of air must be circulated in the tunnels in order to obtain the desired drying or heat setting of the inks.